Studies on Productivity of Rice Plants Growing the North-Marginal Area in Japan : III. Influence of character of seedling on dry matter production and yield

Abstract

In this paper, the relations between the seedling characters and the dry matter production were analyzed using 31 different seedlings. The results obtained were summarized as follows ; 1. The seedling age in leaf number and the ratio of dry matter weight to plant height were the useful parameters to estimate the character of seedling. The seedling character index (SCI) was calculated using following equation : (the seedling age in leaf number) × (the ratio of dry matter weight to plant height). The dry matter weight at each stage of growing and the heading date were significantly correlated with SCI (Fig. 2, Table 1). 2. The grain yield indicated positive correlation with the percentage of ripened grains, but negative correlation with the number of grains (Fig. 3). 3. The number of grains increased with the amounts of nitrogen in rice plant at the heading time and reached to 4.4 × 10⁴/m² in high nitrogen level. SCI indicated positive correlation with the dry matter weight but negative correlation with the nitrogen percentage content at the heading time. Therefore, the correlation between the number of grains and SCI was not significant (Fig. 4, Fig. 5). 4. The percentage of fully ripened grains to fertilized grains was determined by the ratio of the amounts of dry matter production to the number of grains and the dry matter partitioning ratio to the ear. The amount of dry matter production after the heading time and the dry matter partitioning ratio to the ear were correlated with the accumulated temperature for 40 days after the heading date (Fig. 6). 5. From these results, it may be concluded that the percentage of ripened grains was affected considerably, but the number of grains was not affected very much, by the character of seedling (Fig. 7).